The objective of this research is to elucidate the role of tRNA in cellular regulatory mechanisms and to determine the function of the many minor, non-vital tRNA species which have been observed. We intend to identify as many genes as possible which affect tRNA structure. These genes will include both tRNA structural genes, and genes involved in the maturation or modification of tRNA. These genes will be investigated both genetically and biochemically with a view toward determining the effects on cellular physiology that result from destruction or alteration of these genes. Bibliographic references: Kohno, Tadahiko and John R. Roth. Proflavin mutagenesis of bacteria. J. Mol. Biol. 89: 17-32, 1974. Roth, John R. Frameshift mutations. Ann. Rev. Genetics 8: 319-346, 1974.